In order to improve the efficiency of product management, a system in which a tag (TAG) containing information capable of representing characteristics of a product is attached to the product and the tag is recognized in a contact way or a contactless way to manage the product is applied to a POS (Point of Sale) system of a market or a stall, a logistics system, a delivery system and the like.
This system is mainly used to identify an object of the product to be sold or transferred, and is configured so that a tag such as a bar code and a QR code attached to the product is recognized and the recognized information is databased to perform post-processing such as collection, statistics, storage or processing of the information.
Recently, in order to solve inherent problems of the bar code (or, the QR code) that allows recognition of information using an optical signal, namely the recognition distance is short and the recognition is impossible when there is an obstacle between a reader and the tag, a method of recognizing and utilizing a tag of a product remotely in a non-contact way through a radio signal transmission and reception using a NFC tag or a RFID tag (RF tag) is used more and more.
Among them, the RF tag using a RF signal may be classified into a passive type, an active type and a semi-passive type depending on whether the power in the RF tag is used for accessing and reading the information recorded in a tag chip and transmits the read information to a reader.
The technology using RFID (Radio Frequency IDentification) is used in various fields since the RF tag attached to a product (article) is recognized using a radio wave to allow collection, storage and tracking of the information of each product (article). Recently, there is also introduced a method of estimating a location of a RF tag or a product to which the RF tag is attached, by using the received signal strength identification (RSSI) of the RF tag received from a plurality of readers (antennas).
However, this method has a problem that the signal intensity value is distorted under an environment where the signal has low accuracy and is vulnerable to interference because the resolution is low when the signal intensity is not larger than a threshold value.
Moreover, the method of calculating and utilizing the location information using RSSI requires an additional complicated structure for measuring and analyzing the intensity of received signals. For this reason, the conventional system environment using the RF tag is not able to be used as it is, and thus there is an inherent limit in terms of expandability and versatility.
In addition, a method using GPS information is also disclosed as the method of calculating a location of a tag. However, even though this method has an advantage that the location information is relatively accurately calculated, the method should have an additional configuration, which gives the same problem as the method using RSSI. Also, this method is not applicable at all in a room where a signal is not received from a GPS satellite. In addition, if the number of products is large, a GPS module is required for each product, and thus the efficiency is extremely low in terms of cost.